The present invention relates to an arrangement for driving out volatile impurities from the ground water and from ground through which it flows. More particularly, it relates to the arrangement of the above mentioned type in which the driving out is performed by producing a negative pressure in a well shaft extending to the region of the contaminated ground water and supplying a gas, especially fresh air underneath the water level of the well shaft.
Arrangements of the above mentioned general type are known in the art. One such arrangement is disclosed for example in the German document DE-OS 3,625,488. In contrast to the conventional methods, in which pressure air is pressed with considerable energy consumption into the ground which surrounds a well shaft and/or into the ground water collected in the well shaft, with the arrangement disclosed in the above mentioned reference air alone under the action of the negative pressure formed in the water-free region of the well shaft or the action of very low negative pressure is supplied for driving out of the impurities. It has been shown that with relatively low negative pressure, surprisingly high quantities of volatile impurities in gaseous state can be aspirated and a significantly higher efficiency is obtained than in conventional methods. In conventional methods under the action of the high pressure the laminar flows are destroyed and whirling is formed, whereby the efficiency of the arrangement is significantly reduced. Moreover, during pumping-in the pressure air into the ground or pumping-out the ground water, the impurities which are distributed nonuniformly in the ground are driven or pulled to noncontaminated regions.